The cool guy at Fairway Chevrolet looked it up and said replace the switch on the dash
thats what i am going to do
waiting to see if the light comes back on first after DTC TCCM code was cleared and it is 115 in Las Vegas dont want to go out in the heat

 

UPDATE.......
switched the vacume lines 180 on the switch on the firewall and everything works
the guy that had the truck before me took it to a shop that isn't very good
he had all the recepts
had been in the shop for the serv. 4wd light code B2725 I pulled the code
and the P0440 evap. code
the 0440 went away with a fuel filter change
this guy had payed for a new fuel tank and pump

 

It''s fixed I hope
replaced the switch on the dash and replumed some vac lines
switches in 4wd ok

99 S10 4 door
2" schacke rear
t bar crank
31 x 10 x 15 BFGoodrich KM2 Mudd TA's
K&N cold air kit
40 series Flow Master

 

update all is working ok hope it is fixed
i was pulling my hair out trying to get it worked out

 

My Service 4WD light came on yesterday. Also got a SES Light that saying I had a misfire... but I don't recall feeling any of it. I know the truck runs pretty rough in traffic with the AC on so its possible. I don't know if the two lights are connected. I cleared the misfire code but I can't read the 4X4 code.

Got stuck in Las Vegas traffic on the I15N just before Sahara in 115 degree heat. Probably not a good thing huh Dave? lol That's what caused all of this.

 

I would highly doubt that they have anything to do with each other.

 

Yeah, me too. I'm worried that I melted that 4x4 circuit being stuck in traffic. Alot of cars were overheating out there and mine got up there too. Turned off the AC and the engine started to cool back down to normal.
Once I get a break to go see if I can even swap into 4x4 modes I'll come back and research the threads a little more for help. I'll probably post my evidence here.

So I was able to drive the truck a little bit today and was able to create a problem. I'm trying to track down a place that can read the codes from the TCCM to get a better idea. Here's the issue:

Truck cold, I can swap between all 4x4 modes easily. Once its driven for awhile, the service 4wd light comes on. At this point I tried to switch modes and the vehicle would go into 4hi. When trying to get back into 2hi, the truck whined a little and heard the dash board clicking. The 2hi light flashed for quite awhile and then the 4hi light flashed and then remained steady.

When I got back to the house, I tried going into 4lo, and 2hi again while in neutral, stopped. Again, the lights would flash, then fail, then the 4hi would flash and then come on steady.

I turned the vehicle off, waited a few seconds, and turned it back on. The Service 4wd light was not on, and I was able to change 4x4 modes easily as if the engine was cold. Perhaps I hit a bump that caused something to come lose that gets reset after a restart of the engine? I'm not sure... but until I can get these codes read I'm trying to weigh my options.

 

Have you gone through and checked all of the connections in the system (TCCM, dash switch, & encoder motor)?

 

Swartkk,

Reliving this thread again. I went through all the connections on the transfer case and checked out what looked like a moving servo/control arm with rubber boot on it. I noticed all my electrical connectors were not secured with the plastic retaining pins with lanyards. My truck went in for tranny maintenance a few years back and they were shady as all hell, not routing cables back in clamps, etc. I thought I caught all of it but found this.
For the most part they were all connected. Covered in oil though because I've got an oil leak between the tranny and oil pan area.

The TCCM and dash switches look secure with no unusual wear or shorts in the wires. I have not had the light all winter. It seems to only do it on very hot days. We'll see what happens the first hot day of the summer...


I'll be working on it this weekend; clean it up some, try to torque on those bolts for the mating surface of transmission, and reconnect those safety pins.